Need more hot water

[Joe Lee]

Hi!  I have an old 431/12 Aquahot system.  The heat works well but I only have a limited amount of hot water. I think the bonding that connects the copper domestic water pipes to the Aquahot tank has started to loose it’s effectiveness. I’m thinking of adding a 6 gallon 110v hot water system to add a bit more hot water for showers when I have shore power. 
 

Does anyone have any experience with this or do you have a better idea?  The cost to replace the Aquahot is more than I want to spend at this point. So, I’m looking for a cheaper enhancement. 
 

thanks!

Joe

[vito.a]

The Aqua Hot water temperature is largely dependent upon the incoming water temperature. 

If you draw water from your onboard fresh water tank you will find you have a lot more hot water.  

[Hypoxia]

If you are not using the diesel burner and relying on the electric element you will not get enough hot water to keep up with the demand with the single 1650 watt 120 volt element you likely have.  If you are using the diesel burner and not keeping up with demand that would be a different story.

I have the 600 series with to 2000 watt elements and cannot keep up with demand on a 40 degree morning with all heat zones on and a shower.

[Guest Ray Davis]

Vito and Hypoxia are right on.  I'll just add that when we are high in the mtns in Colo the well water is ice cold.  Even my fresh water tank is cold especially when I add water from the ice cold well.  I have toyed with the idea of rigging a way to warm the water in the tank.  On the other hand when we were in Phoenix in July the water coming into the coach was actually quite warm. The Aqua-Hot is a very good system, not perfect by a shot way but what system is.

Life is hardly ever just right.  Thats why some people have an RV, so they can chase comfortable weather.   Like us running from Tx heat to Colo cool or Yuma warmth.        Might not do that this year though, there's currently a lot of uncertainty in the country.

[Xracer]

Are you running the Aqua Hot on diesel?

 

[Dr4Film]

The Webasto diesel burner on your Aqua-Hot 431/12 should provide you plenty of heat and hot water. After all, it is a 50K BTU burner.

Hopefully no one has monkeyed around with the "Tempering" valve which determines the temperature of your hot water being supplied to the faucets.

The temperature of your hot water in the boiler should be almost 200F which is enough to scald any person. That's why they have a Tempering valve which mixes cold water with the 200F hot water to accomplish a temperature around 115F - 123F.

Edited June 1, 2022 by Dr4Film

[Joe Lee]

Thanks everyone!

I have the diesel burner on but can’t get continuity hot water. It’s good for a few mins only. Since my system is old, I believe the material that attached the Cooper piping to the outside of the boiler tank is failing. And, yes, my system has the domestic hot water pipes on the outside of the boiler tank.  Newer models have the piping inside the tank. 
 

It doesn’t sound like anyone has needed supplemental hot water for your systems. I saw some 110v water heaters that are used to supplement hot water under a sink. I was hoping someone would have tried this. I do OK when dry camping, but it would be nice to take a longer shower when I have shore power. 
 

Thanks again for taking some of your time to help me!

Joe
 

 

And, I’m only getting about 115 degrees at the point where the water comes out of the boiler tank. Wish it was almost 200 degrees!  And, this temperature is before it gets to the Tempering Valve. 
 

I have replaced the fluid, tempering valve and the thermostats. 
 

Thanks!

[Guest Ray Davis]

There are several qualified repair men that could tell you what may be wrong. I have not heard of the issue you are thinking may be the problem.  The man I'm familiar with is Roger Berke, he is sort of the senior man out there.

He has a web site with a forum, parts, and etc.  I suggest you look in and maybe contact him.

http://rvhydronicheaterrepair.com/

[Dr4Film]

The number "two" person in the Aqua-Hot industry is John Carrillo who is located close to the Aqua-Hot facility in Colorado.

Both Roger and John are the go-to people when you have Aqua-Hot problems.

Roger was the only person I would let touch my Aqua-Hot for many years when living on the west coast. I now have John Carrillo and a person name Butch who works for the Hitching Post of Ocala do service on my Aqua-Hot systems.

It's highly unlikely that the entire copper loop has lost its conductivity as that loop covers the entire outside of the boiler tank. I am guessing that something else is going on to cause your problem. Has the combustion chamber ever been cleaned of all of the soot and carbon buildup?

Roger or John could point you in the right direction as to your most probable cause. I have never read about anyone have a conductivity issue with the copper tubing and the boiler tank. Leaks, yes, but no lack of conductivity.

The 50/50 mixture in your boiler tank needs to be checked also as that can affect heat transfer.

Edited June 1, 2022 by Dr4Film

[Ivan K]

I see nothing wrong with adding a heater to use park power but am skeptical about the suspected cause. If I look at a picture of mine, there is hardly any of the bonding stuff or a way for it to disintegrate and it works great for us. If it wasn't, I would definitely hear about that 🙂 I think I would check if the stir pump is working too, with burner running.

[Guest Ray Davis]

19 minutes ago, Ivan K said:

I think I would check if the stir pump is working too, with burner running.

I meant to mention the stir pump.  If it's not operating the thermostat will cut the burner off before hardly any water has been heated.  In other words the water in the coil/loop must circulate so all of it is heated.   

Some systems don't have an engine loop but I think yours most likely does,  how about on the hiway do you have hot water then?

[Joe Lee]

And, I’m only getting about 115 degrees at the point where the water comes out of the boiler tank. Wish it was almost 200 degrees!  And, this temperature is before it gets to the Tempering Valve. 
 

I have replaced the fluid, tempering valve and the thermostats. 
 

Thanks!

Stir pump?!?  I didn’t know about that!!  I was led to believe that it was the connectivity issue from John. I can’t wait to see if I can identify the stir pump. 

I do have hot water on the road and I have an engine loop. I don’t think the engine loop pump works. The engine loops switch was disabled by the prior owner and I try to stay out of cold environments or use the block heater.  Does this affect the domestic hot water?
 

John has been great but I’m calling Roger too!!

This is such great news!  
 

I’m so appreciative of all the ideas, website links and repair people contacts. 
 

Thank you!!!

[Dr4Film]

The Stir Pump on your 431/12 is circulation pump B. There is a troubleshooting page (#26) in the Service Manual that describes the steps to check for correct operation.

Here is the link to the manual.

AHE-100-02S-Service-Manual-Rev.-B-9-27-2011.pdf (aquahot.com)

[Guest Ray Davis]

Joe,  I googled aqua-hot stir pump and came up with these threads over on IRV2.  They seem to reinforce the idea that it can be your stir pump 

https://www.irv2.com/forums/f54/hydro-hot-stir-pump-320804.html  

https://www.irv2.com/forums/f278/aquahot-circ-pump-replacement-flush-system-232071.html

[georgecederholm]

16 hours ago, Joe Lee said:

I do have hot water on the road and I have an engine loop. I don’t think the engine loop pump works. The engine loops switch was disabled by the prior owner and I try to stay out of cold environments or use the block heater.  Does this affect the domestic hot water?

Joe,

The engine loop will circulate engine coolant through the Aqua-Hot whenever the engine is running. This will heat the water in the tank and you should generally arrive after a travel day with hot water, without having to run the Aqua-Hot on diesel or electric.

The engine loop pump will circulate engine coolant through the boiler when parked with the furnace on, expecting the heat from the boiler to warm up the engine. The fact that your pump may be inoperable shouldn’t influence your domestic water temperature. 

So, if after a normal travel day you have hot water, it’s likely that the thermal transfer action from the boiler and various loops is working. That would point away from the bonding material for the water, and more toward something like the stir pump, which is needed to even out the boiler temperature since the heat source and thermostat(s) are close together.
 

[Joe Lee]

UPDATE: As always, thanks to each of you for sharing your time and knowledge. It is very much appreciated!
 

As for my lack of continuous hot water from my Aquahot 431/12. I followed the advice shared and I discovered 2 issues:

1) The diode inline on the wire that powers the stir pump was bad. I have a new one ordered and hope to install it on Tuesday. 
2) This same wire that should be attached to the B Zone (B 6 terminal on page 76 of the service manual) was attached to C Zone (C 4 terminal). My B Zone pump is a bit noisy, so I was wondering if the prior owner moved it to the C Zone to use a better pump. So, my question, does the stir pump have to be the B Zone pump or would any of the pumps perform the same “stir” function?

 

Thanks!!!
Joe

[Ivan K]

All the ZONE pumps share the same intake and return so no difference in that part. The only difference would be in which registers inside the coach will get warm. In my case a bath vs living room and in my case there are more registers up front. May not be an optimal situation when trying to cool the coach down at the same time.

[Joe Lee]

Update: I have replaced the wire with the diode that connects the diesel burner to the stir pump.  I ran the hot water and monitored the diesel burner and the stir pump, but these devices didn’t turn on. Also, I ran out of hot water in about 90 seconds.  Then, I ran the heat exchangers in the bathroom and bedroom. My thinking was that this would trigger a drop in temperature of the boiler and the diesel burner would turn on. No luck after about 5 mins. 
 

Question:  Does anyone know how the diesel burner is activated when you need the burner to run to support the Stir Pump and continuous hot water?

 

Thanks!!

[Ivan K]

It will be turned on when the the low temp thermostat passes voltage to the controller but i would guess you knew that. You can jump it for a test. It's behind a sheetmetal cover, 4 of them, for diesel and electric. Of course that assumes the interior switch works.

Figured I add that the temp has to be below 175F and the thermostat is called a control thermostat, ON below 175F until it reaches 200F, approximately.  Top left in the configuration. An other possibility is that the high limit safety thermostat (lower left) is open and you can also jump it, just for a test.

Edited June 8, 2022 by Ivan K

[Guest Ray Davis]

Has the burner been working?   Is the hot water problem a recent development?    

 

[Joe Lee]

Thanks Ivan and Ray!

My hot water problem isn’t new.  I have replaced all 4 thermostats at the recommendation of John, the AquaHot guy. Also, replaced the antifreeze with the Aquahot fluid. The diesel burner will come on with the system is cold. I just can get the burner to turn on to support continuous hot water. 
 

With this forums help, I did see that the wire coming out of the diesel burner and eventually connecting to the Stir Pump was mis-wired. Made the correction, but didn’t have any luck in the diesel burner coming on to help with hot water. (I wrote more about this earlier in this thread)

Last winter, I determined that the electric element wasn’t working at all.  It was just a bad thermostat, but with the diesel burner being the only source is heat, I still didn’t have continuous hot water.

I will try jumping the thermostat next. 
 

Thanks!

[Dr4Film]

Have you stepped through ALL of the Troubleshooting steps for the Aqua-Hot to isolate exactly what your problem may be?

It appears that you have just been throwing darts at the problem hoping that one of them will magically fix your situation.

Those steps are in the service manual which I had posted earlier in this thread. They begin in Section 8 page 45 and run for 5 pages.

[Joe Lee]

17 hours ago, Dr4Film said:

Have you stepped through ALL of the Troubleshooting steps for the Aqua-Hot to isolate exactly what your problem may be?

It appears that you have just been throwing darts at the problem hoping that one of them will magically fix your situation.

Those steps are in the service manual which I had posted earlier in this thread. They begin in Section 8 page 45 and run for 5 pages.

Thanks Dr4Film - you are correct. I haven’t followed all of the troubleshooting steps. Several months ago, I got help from John Carrillo. His support yielded that I needed to have the material that attaches the copper piping to the boiler replaced, so I might as well just do a rebuild at his shop. I’m kinda stuck on the east coast right now, so can’t make it to him. 

This forum renewed my energy to try again and I found the Stir Pump wasn’t wired correctly. (Yay!).  But, now, I can’t figure out why the diesel burner doesn’t turn on before I run out of hot water. 
 

I will start over and follow the steps provided. 
 

Thanks for all the help everyone!

[ok-rver]

Interesting read for someone that does not have and knows very little about an Aqua Hot. One bit of information I was wondering about: How hot is the initial water coming out of the tap and by "running out", does the water go to fresh water tank temperature in the 90 seconds?  I there a way to measure the hot tank (boiler?) temperature assuming the water you are measuring at the tap is in coming from the coil around the tank, not the tank water. Richard mentioned a tempering valve, could this be flakey and not letting hot water thru?